3
The One by Four
One option for the fit but severely time-constrained is to try to get in at least one good interval. That’s the takeaway from a paper I coauthored in 2013 with Ulrik Wisløff, which showed that most of an interval workout’s benefits come from the first sprint. Note that Wisløff’s lab had its subjects conduct a 10-minute-long warm-up and a 5-minute-long cool-down. In the interests of time efficiency I’ve cut down both.
Peak Intensity • 6
Duration • 9 minutes
The Evidence • It’s possible to reduce the risk of death from cardiovascular disease with a lot less exercise than the guidelines suggest. Ulrik Wisløff and his researchers wondered how little exercise was required to provide a benefit—and discovered something surprising. His lab gathered a number of overweight but otherwise healthy middle-age men and divided them into two groups: one conducted the Norwegian protocol of 4 repeats of 4-minute-long sprints; the other conducted just a single 4-minute-long sprint three times a week. After 10 weeks, Wisløff’s lab was surprised to discover that the single-sprint group had experienced most of the benefits of the 4-sprint group. The 4-sprint group boosted its cardiorespiratory fitness by 13 percent, an impressive amount—but the single-sprint group boosted its fitness by nearly as much: by 10 percent. The point? If you don’t have much time, a single sprint can pack a powerful punch.
Who Should Do It? • A 4-minute sprint at an intensity of 6 is no joke. If you find yourself unable to do it, simply start with a shorter sprint and work your way up to 4 minutes over time.
THE WORKOUT
- Warm up with light activity for 3 minutes.
- Conduct the sprint for 4 minutes at an intensity of 6—fast enough to get you breathing hard but not quite gasping for breath.
- Cool down with 2 minutes of light activity.